Transcript
IPES Magnetic Anomalies Geology Unit
Name________________________ 10
Date___________Hr_____
BACKGROUND: Before being widely accepted, a new hypothesis must be tested. One test for the seafloor-spreading hypothesis involved magnetic patterns on the sea floor.
In the late 1950's, scientists mapped the present-day magnetic field generated by rocks on the floor of the Pacific Ocean. The volcanic rocks which make up the sea floor have magnetization because, as they cool, magnetic minerals within the rock align to the Earth's magnetic field. The intensity of the magnetic field they measured was very different from the intensity they had calculated. Thus, the scientists detected magnetic anomalies, or differences in the magnetic field from place to place. They found positive and negative magnetic anomalies. Positive magnetic anomalies are places where the magnetic field is stronger than expected. Positive magnetic anomalies are induced when the rock cools and solidifies with the Earth's north magnetic pole in the northern geographic hemisphere. The Earth's magnetic field is enhanced by the magnetic field of the rock. Negative magnetic anomalies are magnetic anomalies that are weaker than expected. Negative magnetic anomalies are induced when the rock cools and solidifies with the Earth's north magnetic pole in the southern geographic hemisphere. The resultant magnetic field is less than expected because the Earth's magnetic field is reduced by the magnetic field of the rock. From: http://volcano.und.nodak.edu/vwdocs/vwlessons/plate_tectonics/part9.html DIRECTIONS: 1. In the box below, create a magnetic stripe.
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2. In the space below, create a magnetic anomaly wiggle that corresponds with your magnetic stripe above.
3. Tear along the dotted line and give your magnetic anomaly wiggles to a partner, and swap for theirs. Be sure that you don’t see each other’s magnetic stripes! 4. In the box below, create the magnetic stripe that matches your partner’s magnetic anomaly wiggle, while your partner does the same for yours.
5. Once both partners have successfully completed the magnetic stripes, compare your originals with your partner’s stripes. How did you do?
6. Are there any differences? What might account for that?
Geomagnetic Polarity Time Scale Geology Unit
Name________________________ 10
Date________Hr____
DIRECTIONS: 1. Analyze the magnetic anomaly wiggle that you have been given. The black arrow represents the ships route while gathering the magnetic anomaly data. 2. Sketch the corresponding magnetic stripe within the box below. (Note: it may not fill the entire box)
3. Match your magnetic stripe with the geomagnetic polarity time scale on the next page to determine the time span that your wiggles represent. 4. Compare your prediction with those of your team members. Once you believe you have correctly determined the time frame for your magnetic stripe, your team is to put their stripes in chronological order. 5. Ask your teacher if your team has successfully put the pieces of the puzzle together.
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Geomagnetic Polarity Time Scale Cande & Kent 1995
